1. Field of the Invention
The invention relates to an arrangement in constituting a power supply for supplying the heating coils of a tube, in particular a traveling-wave tube, wherein a transformer and an inverter are provided in the heating circuit of the tube.
2. Prior Art
As a rule, power amplifier tubes, in particular traveling wave tubes, are operated via current limiting regulators in the heating circuit, so that the heating current cannot increase to impermissible values. Such current limiting regulators in the heating circuit are known, for example, from U.S. Pat. No. 4,267,487 or from the pamphlets "Space Amplifier at 20/30 GHz", ANT 15 06 aE, 05.84; "Traveling Wave Amplifiers (TWTAs) for Space Applications" ANT 776 841, 09.90 of the firm ANT Nachrichten-technik GmbH.
In a voltage regulator known from U.S. Pat. No. 4,257,089, the frequency of a push-pull switching regulator is varied as a function of an error voltage on the output side. Thus, with a large error deviation, less energy is transmitted to the load.
In the limitation device in accordance with U.S. Pat. No. 4,267,487, the tube is supplied with DC current. AC components are suppressed in that the voltage at the heating filament is detected and a negative feedback signal is generated which controls an impedance in the supply circuit.
In a device known from the IEEE Conf. Rec. of the 1988 18th Power Modulator Symposium, pages 269-273 "Filament Considerations for High Stability Radar", the fluctuations in the heating voltage caused by frequency changes of the heating current are suppressed by a special coil geometry of the secondary coil of a HV transformer.